Radius-in-image dependent detector row filtering for windmill artifact reduction

a detector row and windmill technology, applied in tomography, instruments, applications, etc., can solve the problems of aliasing artifacts in reconstructed images, insufficient sampling intervals in the z-axis (detector row) direction, and data size double the size of current us

Inactive Publication Date: 2005-10-13
KK TOSHIBA +1
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Problems solved by technology

One common problem with cone beam or quasi-cone-beam algorithms is insufficient sampling intervals in the z-axis (detector row) direction.
These algorithms violate the Nyquist theorem (which requires two samples within one detector cell aperture) and causes aliasing artifacts in reconstructed images due to high frequency components.
However, this potential solution has the following disadvantages: (1) the data size becomes twice as l

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  • Radius-in-image dependent detector row filtering for windmill artifact reduction
  • Radius-in-image dependent detector row filtering for windmill artifact reduction
  • Radius-in-image dependent detector row filtering for windmill artifact reduction

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[0026] The sharpness of the kernel increases with decreasing r2D (e.g., a projected distance from the iso-center to the ray-sum onto the xy-plane), so that pixels near an iso-center have better z-resolution than in the periphery. Thus, the cause of the windmill artifact at the peripheral regions may be suppressed by applying a smoothing kernel to the corresponding detector channels.

[0027] To this end, filter data in a detector row direction may be obtained prior to image reconstruction. The kernel of the filter may be defined as a function of the ray-angle. That is, the kernel may be adjusted based on the projected distance from the iso-center to the ray-sum onto the xy-plane. Equation 1 (below) provides the desired function: pout⁢ ⁢(v,ch,row)=∑k=-KK⁢[wGn⁡(k,ch)·pin⁢ ⁢(v,ch,row+k)](1)

In Equation 1, pin is the projection data, v represents the projection number index corresponding to the projection angle β, ch is the detector channel index corresponding to the ray angle γ, row is ...

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Abstract

A method, X-ray CT apparatus, and computer program product for obtaining data from a computed tomography (CT) scan, wherein projection data are obtained from at least two detector rows in a CT system, the projection data are filtered in a direction of the at least two detector rows to obtain filtered data in which windmill artifacts are reduced, and the filtered data are reconstructed.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] Multi-slice x-ray computer tomography (CT) systems were developed and introduced into the medical market around 1998. The number of slices generally ranges from 2 to 40 currently, and is expected to increase to 64 or even 256. (See Y. Saito, H. Aradate, H. Miyazaki, K. Igarashi, and H. Ide, “Development of a Large Area 2-dimensional Detector for Real-Time 3-dimensional CT (4D-CT),”Radiology vol. 217 (P), 405 (2000); Y. Saito, H. Aradate, H. Miyazaki, K. Igarashi, and H. Ide, “Large Area Two-Dimensional Detector System for Real-Time Three-Dimensional CT (4D-CT),”Proc. of SPIE Med. Imag. Conf., 4320, 775-782 (2001); and http: / / www3.toshiba.co.jp / medical / 4d-ct / , the contents of each of which are herein incorporated by reference). One cone-beam image reconstruction algorithm with helical scanning for CT systems uses a generalized weighted version of Feldkamp reconstruction algorithm, which introduces a flexible focus or...

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Application Information

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IPC IPC(8): A61B6/00A61B6/03G01N23/00G01N23/04G21K1/12H05G1/60
CPCA61B6/032G01N23/046G01N2223/419A61B6/4021A61B6/027
Inventor TAGUCHI, KATSUYUKI
Owner KK TOSHIBA
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